An error compensation scheme is used to secure communication reliability. Examples of the error compensation scheme include a forward error correction (FEC) scheme and an automatic repeat request (ARQ) scheme. In the FEC scheme, errors in a receiving end are corrected by attaching an extra error correction code to information bits. The FEC scheme has an advantage in that time delay is small and no information is additionally exchanged between a transmitting end and the receiving end but also has a disadvantage in that system efficiency deteriorates in a good channel environment. The ARQ scheme has an advantage in that transmission reliability can be increased but also has a disadvantage in that time delay occurs and system efficiency deteriorates in a poor channel environment.
A hybrid automatic repeat request (HARQ) scheme is a combination of the FEC scheme and the ARQ scheme. In the HARQ scheme, it is determined whether an unrecoverable error is included in data received by a physical layer, and retransmission is requested upon detecting the error, thereby improving performance.
If the error is not detected from the received data, a receiver transmits a positive-acknowledgement (ACK) signal as a reception acknowledgement to report to a transmitter that reception is successful. If the error is detected from the received data, the receiver transmits a negative-acknowledgement (NACK) signal as the reception acknowledgement to report to the transmitter that the error is detected. The transmitter can retransmit the data upon receiving the NACK signal.
Long term evolution (LTE) based on 3rd generation partnership project (3GPP) technical specification (TS) release 8 is a most dominant next mobile communication standard.
The 3GPP LTE supports hybrid automatic repeat request (HARQ) in both uplink transmission and downlink transmission. Downlink HARQ implies that, when a base station (BS) transmits downlink data, a user equipment (UE) transmits an ACK/NACK signal for the downlink data. Uplink HARQ implies that, when the UE transmits uplink data, the BS transmits an ACK/NACK signal for the uplink data.
In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) that is an evolution of the 3GPP LTE. An LTE-A system employs new techniques such as carrier aggregation, relay, and uplink multiple input multiple output (MIMO).
The carrier aggregation is used to flexibly extend an available bandwidth. The 3GPP LTE uses one component carrier, and supports up to a 20 MHz bandwidth. The carrier aggregation includes a technique for supporting a 100 MHz system bandwidth by using a plurality of component carriers and a technique for allocating an asymmetric bandwidth between an uplink and a downlink.
In control channels of the 3GPP LTE, an HARQ is designed based on a single carrier component. With the introduction of the carrier aggregation, there is a need for a method capable of performing the HARQ by using a plurality of component carriers.